In any manufacturing business, profitability depends in part on the extent to which the conversion of raw materials into finished products is optimized. This is particularly true in the wood products industry where raw logs are cut into lumber. Currently, the decision of how to cut lumber from a log is made by having a human operator visually grade a log based on such features as the number of knots in the log, the straightness of the log, any rot, etc. Next, the log is scanned using lasers or other sensors to determine its shape and dimensions. Given the grade of a log, a price table is selected and used by the sawing system's optimizing computer to calculate the assortment of lumber sizes that maximizes the value recovered from the log. The price tables are based on lumber market values, historical sawmill recovery data and may also take into account market demand by grade and dimension.
While this method works well for sawmills selling only visually graded lumber, it does not work well for mills wanting to sell various grades of higher-valued stress-rated lumber. For instance, it is well known that for some dimensions, lumber having a high modulus of elasticity (MOE) or stiffness is worth more than lumber with a low MOE. Boards having a high MOE and appropriate strength properties can be used in such applications as floor joists or roof trusses where such properties are desired. However, the relation between stiffness and price is not always straightforward. For example, 2".times.8"boards are very desirable if they meet certain stiffness and strength criteria, but not very desirable if they do not. Having an advance estimate of the structural properties of the wood allows the sawing optimization system to avoid making low stiffness/strength 2.times.8 lumber, and instead making either 2.times.6 or 2.times.10 lumber where the price penalties for lower structural properties are less pronounced. In the past, there has not been a practical way to predict the MOE of lumber to be produced from a log and to take the predicted MOE into consideration when making cutting decisions.
Given the shortcomings in the art, there is a need for a system that can determine and consider the potential stiffness of lumber to be cut from a log in addition to the conventional measurements of shape and dimensions in order to make a cutting decision that will maximize the profit to be made from an individual log.